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Metal–organic frameworks (MOFs) necessitate buffers or basic amine moieties for high activity and turnover in the hydrolysis of organophosphates. While polymeric amine buffers can be integrated with a MOF, all solid-state formulations suffer from active site poisoning of the secondary building units (SBUs) within MOFs which inhibits further catalytic turnover. Herein, we developed a simple soaking procedure with a basic aqueous solution that reactivates the active sites of spent MOFs after organophosphate catalysis. Moreover, we develop amine functionalized MOF-808 derivatives through de novo synthesis with H3-BTC-NH2 (BTC = 1,3,5-benzenetricarboxylic acid) and post-synthetic modification (PSM) that are highly active for organophosphate hydrolysis under non-buffered aqueous conditions. [ABSTRACT FROM AUTHOR]

Abstract: UiO‐66 is a highly stable metal‐organic framework (MOF) that has garnered interest for many adsorption applications. For small, nonpolar adsorbates, physisorption is dominated by weak Van der Waals interactions limiting the adsorption capacity. A common strategy to enhance the adsorption properties of isoreticular MOFs, such as UiO‐66, is to add functional groups to the organic linker. Low and high pressure O2 isotherms were measured on UiO‐66 MOFs functionalized with electron donating and withdrawing groups. It was found that the electron donating effects of ‐NH2, ‐OH, and ‐OCF3 groups enhance the uptake of O2. Interestingly, a significant enhancement in both the binding energy and adsorption capacity of O2 was observed for UiO‐66‐(OH)2‐p, which has two ‐OH groups para from one another. Density functional theory (DFT) simulations were used to calculate the binding energy of oxygen to each MOF, which trended with the adsorption capacity and agreed well with the heats of adsorption calculated from the Toth model fit to multi‐temperature isotherms. DFT simulations also determined the highest energy binding site to be on top of the electron π‐cloud of the aromatic ring of the ligand, with a direct trend of the binding energy with low pressure adsorption capacity. Uniquely, DFT found that oxygen molecules adsorbed to UiO‐66‐(OH)2‐p prefer to align parallel to the ‐OH groups on the aromatic ring. Similar effects for the electron donation of the functional groups were observed for the low pressure adsorption of N2, CH4, and CO2. [ABSTRACT FROM AUTHOR]

Carbon dioxide adsorption in metal-organic frameworks has been widely studied for applications in carbon capture and sequestration. A critical component that has been largely overlooked is the measurement of diffusion rates. This paper describes a new reproducible procedure to synthesize millimeter-scale Cu-BTC single crystals using concentrated reactants and an acetic acid modulator. Microscopic images, X-ray diffraction patterns, Brunauer-Emmett-Teller surface areas, and thermogravimetric analysis results all confirm the high quality of these Cu-BTC single crystals. The large crystal size aids in the accurate measurement of micropore diffusion coefficients. Concentration-swing frequency response performed at varying gas-phase concentrations gives diffusion coefficients that show very little dependence on the loading up to pressures of 0.1 bar. The measured micropore diffusion coefficient for CO2 in Cu-BTC is 1.7 x 10-9 m²/s. [ABSTRACT FROM AUTHOR]

A strategy is developed to enhance the barrier protection of polyethylene oxide (PEO)-metal-organic framework (MOF) composite films against chemical warfare agent simulants. To achieve enhanced protection, an impermeable high-aspect-ratio filler in the form of Laponite RD (LRD) clay platelets was incorporated into a composite PEO film containing MOF UiO-66-NH 2 . The inclusion of the platelets aids in mitigating permeation of inert hydrocarbons (octane) and toxic chemicals (2-chloroethyl ethyl sulfide, 2-CEES) of dimensions/chemistry similar to prominent vesicant threats while still maintaining high water vapor transport rates (WVTR). By utilizing small-angle neutron scattering, small-angle X-ray scattering, and wide-angle X-ray scattering, the LRD platelet alignment of the films was determined, and the structure of the films was correlated with performance as a barrier material. Performance of the membranes against toxic chemical threats was assessed using permeation testing of octane and 2-CEES, a common simulant for the vesicant mustard gas, and breathability of the membranes was assessed using WVTR measurements. To assess their robustness, chemical exposure ( in situ diffuse reflectance infrared Fourier transform spectroscopy) and mechanical (tensile strength) measurements were also performed. It was demonstrated that the barrier performance of the film upon inclusion of the LRD platelets exceeds that of other MOF-polymer composites found in the literature and that this approach establishes a new path for improving permselective materials for chemical protection applications.